The present invention relates to a process for manufacturing niobium plates or sheets as well as uses thereof, such as for deep drawn cups and sputtering targets.
Niobium ingots can be rolled to plate and sheet dimensions using known methods in the art. Such plates and sheets can be used, for example, by being deep drawn into cups for the synthetic diamond industry. The niobium foil used typically has an inconsistent and coarse grain size, which leads to poor flatness and smoothness of the deep drawn cup bottom. Poor flatness and/or smoothness (orange peel) result in a synthetic diamond that requires excessive grinding to correct deficiencies. The problem ultimately relates to a coarse grain structure in the niobium sheet. The coarse grain structure can also cause tearing of the sheet during deep-draw operations.
The grain size of typical, commercially available niobium sheet is variable, ranging from an ASTM grain size of from 4 to 10. It is, however, desirable to use niobium sheet with an ASTM grain size finer than 7.5 with at least 90% recrystallization for deep draw applications, although this still produces a high rejection rate for flatness and surface finish. An ASTM grain size finer than 8.0 with at least 90% recrystallization almost completely eliminates these issues.
It would be desirable to provide a method of producing niobium sheet having a consistent ASTM grain size and sufficient recrystallization to minimize or prevent flatness and/or smoothness problems with the sheet.
U.S. application Ser. No. 10/974,519, filed Oct. 27, 2004 describes a silicon-containing alloy of niobium that solves the above-identified problem.